When you're starting your shift at your coffee shop and take over the bar from another barista, the machine and grinder can be in varying states of cleanliness and calibration. How do you quickly and correctly get back to pulling good shots from clean equipment?

2 Answers 2


This answer addresses a "standard" semi-automatic espresso machine with a separate grinder. Specifically the LaMarzocco and Astoria grinder, but the ideas should generalize to other machines of the same class.


Of course, wipe down everything and get all pitchers and spoons clean. Blast out all the milk and "wetness" from the steam wands. Inspect and clean all portafilters* (get one clean, and then use it while you clean the others), and if necessary backflush the groups with water (with "bumping" so you blast water around the seals to get any buildup there clean).

*especially under the basket.


The abstract procedure here is described using the Hackers' terms Frob, Twiddle, and Tweak.

frob quote from Hackers' Dictionary

To fully calibrate the setup, we'll need to make three passes over all the controls.

  1. Frob. In the frob pass, we make just "coarse" adjustments to get everything roughly correct. (reinterpreting the hacker usage. This isn't aimless.)
  2. Twiddle. In the twiddle pass, we adjust each parameter up and down a little, in a more "scientific" manner: while adjusting any one parameter, the rest are left alone so they behave as "controls" for the quick little "experiments" to check each change.
  3. Tweak. In the tweak pass, everything should be mostly correct by now. Just apply any finishing touches.

The controls we have available are the grind, dose, and water quantity. Following the David Schomer method, I strongly advise that the tamping pressure should be constant. Always tamp the same way: from the elbow, so you don't stress your wrists.

In the David Schomer method, the dose is controlled by counting "clicks" of the doser. You keep the doser compartment as empty as possible, grinding only what you need so everything stays fresh, locked in the bean). Count how many clicks gets you to "full", maybe a little heaping. This number is your base dose. Keep it constant for now. And this constitutes the "frob" of the dose.

Set the group in programming mode and Pull a shot, setting the water level to yield 2 oz. This is the "frob" of the water quantity.

If the extraction time was off, adjust the grind. This the "frob" of the grind, so you can make bigger movements if you need to (exercise your judgement), but remember only adjust finer while grinding, so you don't lock the burrs on a tough bean. Pull a few shots until the time is (roughly) correct.

So, we've done our "frob" pass. Now "twiddle." Adjusting the grind to control the extraction time probably threw off the water quantity a little bit. So do a "twiddle" of the water quantity by entering programming mode and pulling a shot. Actually, you shouldn't need to "twiddle" per se: there's no *up and down" here, but I think the terms still represent a useful mnemonic for the general procedure.

Then do a "twiddle" of the grind. You want the grind to be as coarse as possible within its "range", if you know what I mean. All the grounds in the doser are quickly going stale. A coarser grind yields little pieces of coffee bean that are slightly larger, with a lower surface/volume ratio. Lower surface area means less interaction with the air, and the grounds resist going stale a little better.

There should be no need to "twiddle" the dose at this point. We're adjusting the other controls so the dose remains at comfortable spot.

Now, one final pass to "tweak". Pull a shot, and examine its quality. Particularly look for the tell-tale white "overextraction stain" where the last drips struck the crema. You want to tweak the water quantity to stop just before the color changes. This tweak gives you "ristretto-quality" shots.

Adjusting on-the-fly

Remember that we did not mess with the dose much in the above steps. But the other parameters were setup so the dose is "comfortable". This lets us make small adjustments to the dose in order to "ride the wave" of the machine and keep all the shots in the time range. Remember not to brew shots while the boiler is cycling.

The same three adjustments, frob, twiddle, and tweak, apply also to dynamic adjustments. Frob, the coarsest control is the water quantity, which should no longer need adjusting at this point. Twiddle, the medium-grain control is the grind setting. Unless a freak thundershower rolls-in and totally changes the pressure and humidity of the atmosphere, you should only need to make small adjustments and only to recalibrate the dose to a comfortable level. Tweak, the finest control is the dose.

If a shot pulls 1-second too long, tweak your dose ever-so-slightly shorter. Either count 1-fewer click, or count your clicks just a hair faster.

If a shot pulls 1-second too short, tweak your dose ever-so-slightly longer. Either count 1 more click, or count your clicks just a hair slower.

If the dose gets too low (by visual inspection: exercise your judgement), twiddle the grind a little coarser so you can achieve the same density with more mass.

If the dose gets too high (exercise judgement), twiddle the grind a little finer so you can achieve the density with less mass. (Volume is constant.)

I actually haven't worked on this machine in almost 10 years. So this is all based on my memory of that one amazing day when I pulled 20sec (+/-1) shots for eight solid hours.

On a different day, I recalibrated after a thunderstorm started by pulling the grinder 8 clicks (!) coarser. And got it back to 20sec after 2 or 3 pairs.

That's how I know. But I learned this all from David Schomer's book.


Appendix: The "David Schomer" method or "ritual"

This is what I remember from the amazing book, Espresso Coffee: Professional techniques by David Schomer. And hey Matt, I want my copy back!

A. Preheat and Clean.

  1. Pull an ounce or so of water through the old spent puck to heat the group.

  2. Yank the portafilter and knock the old puck into the compost bin.

  3. Wipe the basket and run a splash of water through the group without the portafilter to rinse the upper screen. (You can catch this water with the portafilter before wiping to rinse more of the grounds so your clean towel stays clean longer.)

B. Grind and Dose.

  1. Turn on grinder to start to fill the doser (which should be as empty as practical).

  2. Immediately start pulling clicks of the doser until the basket is full, or a little heaping.

  3. Turn off grinder.

C. Distribute and Tamp.

  1. With clean hands, distribute the grounds evenly with a finger (I use my ring finger, but whatever works).

  2. Tamp lightly to shape the puck.

  3. Tap the edge with the handle end of your nice aluminum tamper that you bought yourself and brought to work to help. This gets the little bit of coffee around the edge that the tamper missed.

  4. Tamp firmly, from the elbow. About 30 pounds of pressure.

  5. Reinsert the portafiler.

D. Brew.

  1. Click the button to start brewing.

  2. Immediately discard the hot water from the shot glasses which is still there from step A.1.

  3. Watch the pour and stop it early if you need to, to catch the sweet spot.

And finally, I apologize for my excessive use of emphatic "quotation marks".


This answer addresses a Super-Automatic machine with built-in automatic grinder/doser/tamper. Specifically the Starbucks Mastrena machine, but the ideas should generalize to other machines of the same class.


Pull the grind back XX clicks coarser (XX=5 small recalib., XX=10 big recalib., XX=20 emergency (piston/powder errors -- but call service on it, too)).

Keep pulling pairs until it settles down to running consistent shots (howsoever fast). Check for dry pucks in the drawer.

Take it back up. Repeat: (Pull 1 pair of shots, Turn 1 click finer). Stop turning finer at 16 or 17 and it will ride up to 18-23s. (Mnemonic: "blackjack house rules".)


You should always be rinsing. You are not done rinsing until the water runs clear.

The water you see is the water you were about to brew with. Don't brew with brown water!


If the machine is acting up, give it a cleaning cycle. If a coworker challenges you, ask them why they want to serve bad shots??! Or better, calmly explain that it's the obvious thing to do to get back on track. Unpredictable shots == unpredictable drink production times.

If you cannot take the machine down for a cycle (it's too busy at that moment), the following should help, but is no substitute.

Super-automatics that have run hot all morning and then sat relatively idle through midmorning and then run hot again for the after-lunch crowd have what I call the "oatmeal bowl problem". If you eat some oatmeal and don't rinse the bowl right away, what happens? You know what happens! It gets hard. It becomes a crust. The same thing happens inside the machine. You need to run a cleaning cycle. For reals, dog.

Extending the analogy, suppose your friend drops by to borrow that book and you've had three bowl of oatmeal already and you offer your friend a bowl... You wash the bowl first ... right?

Break it down.

Step 1 of breaking down a machine is the pill.
Step 1 of breaking down a machine is the pill.
Step 1 of breaking down a machine is the pill.

I repeat:
Step 1 of breaking down a machine is the pill.

While it's pilling, you can soak the steam wand (all the way up past the holes at the top, tube removed.), and remove the hoppers and vacuum the grinders.

Wipe out the oils from the grinders with a napkin or paper towel (no water up there!)

When it's done pilling, you can take the drawer and the tray and the spout to wash.

Vacuum and/or wipe grounds from the carcass and reach up with a towel and clean the two ribs.

Then, clean the heart. Just between the ribs there are two circles, one on your side and one a few inches away on the other side. With a towel, wipe any crusty stuff from the edges of the two circles. These are the two halves which come together to form the brewing chamber, the crucible of the alchemy.

If you really want to treat your machine (maybe it's the machine's birthday), give it another pill before bringing it back up. Blast out the steam till it's nice and dry. Scrape and remove all the milk residue until its just shiny shiny metal. Bottle-brush the steam tube.

Deep-cleaning the steam wands

Then give its buddy some love.


I'm assuming you don't have access to the real programming mode. So the controls here are very, very limited. You can adjust the grind, rinse, and pull shots with one of several programmed buttons.

Each programed button maintains a log of the parameters and measurements of the last few shots upon which it performs some simple statistical analysis to determine when to print "adjust grind coarser" or "adjust grind finer" on the screen. So, the machine only "sees" a problem when it becomes a big problem. And it's not designed to respond to (or even detect) "too much inconsistency". Conquently, always prefer the Log View which shows you the actual numbers to the standard view which only shows you the approximate extraction time averaged over the last several (about 5, I think) shots. On the Mastrena machine, switch to Log View by pressing the Up and Down buttons at the same time; switch back to normal view by pressing Cancel. (You can still queue shots but pressing Cancel to switch back to normal view will also remove the last queued shot just as it does on normal view.)

If the numbers are "too inconsistent" (exercise your judgment), then you really need to run a cleaning cycle before trying to calibrate.

Alright, to actually calibrate a programmed button on a clean machine, take the grind a few clicks coarser than you think it should be set. Coarser flakes will help to scrub the doser channels between the grinder and the brewing chamber. With a very fine grind, the heat and moisture from the nearby brewing chamber will contribute to caking in the doser. That gives you a non-linear response from grind-time-adjustment/extraction-time-result. And it is this which I believe is the cause of the usual "death-spiral" of a Super-Automatic before it needs servicing.

If it's acting really bad, you may need to go more-than-a-few clicks coarser. Following my own advice today took a lot longer than the official "10 clicks coarser, pull 10 pairs, then adjust by pulling 3 pairs between each grind change" that we currently follow (when I'm not around) probably would have done.

So, you've adjusted to a very coarse grind. Pull 3 or 4 (pairs of) shots, then start adjusting the grind finer 1 click at a time, then pull a shot. 1 click, 1 shot, 1 click, 1 shot. Then just follow house-rules for blackjack. Stand on 16 or 17.

It takes 2 or 3 pairs for a grind adjustment to take effect, depending upon the length of the doser channel in the particular kind of machine. So by the 1-click,1-shot cycle above, we have a 1 or 2 shot backlog of having adjusted finer. This will ride up to about 20sec shots if everything else is normal. So we stop adjusting when the shot times hit the bottom of the desired range.

How to know if you've gone coarse enough

The signs I've been looking for (which I kept not getting today) is a run of short shots at around 10sec that all look the same and leave the shot glasses mostly clear at the second rinse. I also look to see if its producing dry pucks in the drawer. If the puck explodes into mush, that's what we used to call a shot that didn't "catch" on the old machines.

Run of short shots + clean at the second rinse + dry pucks == take it back up.

Cross-Calibrating single-shot and double-shot programs at the same grind

If you have single-shot and double-shot buttons which use the same grinder, then it's possible to have the singles pulling long with the doubles pulling short or any combination of good, bad, and ugly in between.

The procedure that seem to be working for me is to calibrate the longest program to be correct, and let the machine self-adjust the short program to compensate.

Always, always, always, calibrate from the coarse side of things. This keeps the doser and brewing chamber scrubbed and avoids caking which leads to unpredictable results.

Adjusting on the fly

I posted this idea some years ago in facebook.

I've begun to notice a pattern in the shot times on the Mastrenas. The first pair from a run are short, because the brewing chamber is relatively cold. As the chamber heats, grinds begin to accumulate on the interior, increasing the effective dose (therefore proportion, therefore density), progressively pulling longer and muddier shots.

So, aside from rinsing like fanatics as you all already ought to do. You can: Before the first shot, click it finer. About 2 pairs into the run, click it back coarser. 4 or 5 pairs after that, click it one more coarser. This is your "cruise" setting.

Larger flakes should act more like "fiber" and keep the chamber scrubbed. But you need to go finer at the start to compensate for lower temperature.

If it's been a long time (>15 minutes), then your first pair are not only cold but stale. If it's your mom, don't serve her those shots.

Unlike the Verismos (and the Astorias, too, for that matter), these Mastrenas seem to have a very small doser so the effect of grind-change is quite rapid. This first pair will be a blend of the old setting and the new. The second pair is most or all fresh ground.

Unresolved issues

The triple shot button. Right now on one machine we have the single part grinding longer than the double part, and I don't know how to get them untwisted.

Piston/Position/Powder Errors

Call Service! But also, try this until they get there:

  1. Cross your fingers.
  2. Pull a decaf single.
  3. Rinse.
  4. Throw a pinch of cinnamon over your shoulder.
  5. Rinse again.
  6. Pull a half-caff double.
  7. Rinse again.
  8. See "Emergency recalib, above.

[n.b This is not official Starbucks policy, but my own private theory developed over the past 10 years of working with this machine (and its predecessor the Verismo). Other Starbucks Baristas should follow this advice only if comfortable with having to explain what you're doing to the other Baristas (and Managers) who may be staring at you wondering what you think you're doing.

So, look out for yourselves.]

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